Chapter 34 Integration and Control: Nervous System

Communication Lines Stimulus (input) Receptors (sensory neurons) Integrators (interneurons) motor neurons Effectors (muscles, glands) Response (output)

Invertebrate Nervous Systems All animals except sponges have some sort of nervous system Nerve cells are oriented relative to one another in signal-conducting and information- processing highways

Nerve net Nerve Net

Bilateral nervous systems Bilateral Nervous Systems

Central and Peripheral Nervous Systems Central nervous system (CNS) Brain Spinal cord Peripheral nervous system (PNS) Nerves that thread through the body

Peripheral Nervous System Somatic nerves Motor functions (Shown in green) Autonomic nerves Visceral functions (Shown in red) Controls Smooth,cardiac muscles glands

Sympathetic Nerves Originate in the thoracic and lumbar regions of the spinal cord Ganglia are near the spinal cord Promote responses that prepare the body for stress or physical activity fight-or-flight response

Parasympathetic Nerves Originate in the brain and the sacral region of the spinal cord Ganglia are in walls of organs Promote housekeeping responses digestion

Sympathetic and Parasympathetic Nerves Autonomic nerves

Vertebrate nervous system divisions Vertebrate Nervous Systems

Vertebrate Brains Human brain development

Vertebrate Brains 3 areas of the brain Hindbrain regulates organs below level of consciousness coordinates motor activity Midbrain Forebrain receives sensory input from midbrain and hindbrain  regulates their output optic lobes  coordinating reflex responses

Vertebrate Brains Regions of the vertebrate brain

Three Classes of Neurons Motor neurons efferent take info from the CNA take impulses from CNS to muscles and glands have many dendrites and a single axon (multi- polar) Sensory neurons Afferent take info to the CNS unipolar

Neurons

Motor Neuron dendrites cell body Input Zone Trigger Zone Conducting Zone axon Output Zone axon endings

Three Classes of Neurons Inter-neurons occur within the CNS multi-polar account for complex pathways that account for thinking memory language

Neuroglia 2 types of Neuroglia microglia remove bacterial and debris astrocytes provide metabolic and structural support

Function of the Spinal Cord Expressway for signals between brain and peripheral nerves Sensory and motor neurons make direct reflex connections in the spinal cord Spinal reflexes do not involve the brain

Spinal Cord Organization of the spinal cord

Measuring membrane potential Membrane Potential

Transmission of Nerve Impulses Voltage is a measure of the electrical potential difference between 2 points one placed inside and another placed outside the axon Resting potential axon isn’t conducting an impulse directly related to Na and K present normally higher concentration of K within axon  due to active transport  sodium / potassium pump

Ion Concentrations: Resting Potential Potassium (K + ) higher inside than outside Sodium (Na + ) higher outside than inside

Ion concentrations Ion Movement

Action potential propagation Action Potential

Transmission of Nerve Impulses Action Potential rapid change in polarity gated ion channels open / close in response to stimuli during depolarization many more Na ion gates open change in polarity causes Na channels to close and K channels to open as a result re-polarization occurs

All or Nothing All action potentials are the same size If stimulation is below threshold level, no action potential occurs

Repolarization Once peak depolarization is reached, Na + gates close and K + gates open Movement of K + into the neuron repolarizes the cell The inside of the cell once again becomes more negative than the outside

Chemical Synapse Gap between the terminal ending of an axon and the input zone of another cell synaptic vesicle plasma membrane of axon ending of presynapic cell plasma membrane of postsynapic cell synaptic cleft membrane receptor

Synapse function Synaptic Transmission

Synapse axon terminal is in close proximity to the dendrite of another neuron small gap between neurons is called synaptic cleft nerve impulse must be carried across the synaptic cleft via a neurotransmitter stored in synaptic vesicles

Synaptic Transmission Action potential in axon ending of pre- synaptic cell causes voltage-gated calcium channels to open Flow of calcium into pre-synaptic cell causes release of neurotransmitter into synaptic cleft

Synaptic Transmission Neurotransmitter diffuses across cleft and binds to receptors on membrane of postsynaptic cell Binding of neurotransmitter to receptors opens ion channels in the membrane of postsynaptic cell

Chemical synapse Chemical Synapse

muscle fiber axon ending Fig b, p.581

Types of Neurotransmitters Acetylcholine (Ach) excites skeletal muscle inhibits cardiac muscle Norepinephrine (NE) important in dreaming, waking, mood, respond to stress Epinephrine adrenalin Dopamine emotions, learning, attention, fine motor skills

Types of Neurotransmitters Serotonin thermoregulation, sleeping, emotions, perception GABA gamma amino acid butyric acid inhibitor of neurotransmitters released by other neurons Postsynaptic membrane contains enzymes that rapidly inactivate the neurotransmitter acetycholinesterase (Ache)

Neurotransmitter Imbalances Stimulants increase alertness and body activity, then cause depression caffeine nicotine  mimics acetylcholine  affects skeletal muscle activity cocaine / Heroin  blocks neurotransmitters reuptake  affects dopamine levels

Fig a, p.595 PET Scan Cocaine's long term effect

Neurotransmitter Imbalances amphetamines & Ecstasy  induce dopamine release Depressants lower activity of nerves and parts of the brain low level of serotonin Parkinson’s lack of dopamine Alzheimer’s lack of acetylcholine

Fig a, p.582

Neurotransmitter Imbalances Hallucinogens and Marijuana skew sensory perception by interfering with action of neurotransmitters LSD affects action of serotonin marijuana is a depressant at low dose it can also cause disorientation, anxiety, delusion, and hallucinations

Nerve structure Nerve

Ion Flow Ion flow in myelinated axons

Stretch Reflex Stretch reflex

Lobes of the Cerebrum Temporal Frontal Parietal Occipital Primary motor cortex Primary somatosensory cortex Figure Page 590

Vertebrate Brains Sagittal view of a human brain

Limbic System Controls emotions and has role in memory (olfactory tract)cingulate gyrusthalamus amygdala hippocampus hypothalamus Figure Page 591

Limbic System Receiving and integrating areas

Limbic System Limbic system dissection